1. Field of the Invention
The present invention relates to an ink tank used for an ink jet recording apparatus.
2. Related Background Art
The ink jet recording apparatus is a recording apparatus of the so-called non-impact type, which is capable of recording on various recording mediums at high recording speed. Also, with the advantage, among some others, that almost no noise occurs at the time of recording, it is widely used. The ink jet recording apparatus of the kind performs recording on a recording medium by discharging fine ink droplets from minute nozzles, and it has, in general, an ink jet head provided with nozzles for discharging ink droplets and an ink tank that retains ink to be supplied to the ink jet head.
The conventional ink tank used for the ink jet recording apparatus is structured to adjust pressure exerted on ink in order to keep the ink supply from the ink tank to the ink jet head in good condition. For example, the structure is arranged to contain ink absorbent in the ink tank. When the ink tank having ink absorbent contained therein, it is arranged to keep ink in the ink jet head not to fall off from the ink discharge ports by holding the ink absorbent always in the negatively pressurized condition after taking into consideration the difference of water heads of the ink liquid surfaces in the ink discharge ports of the ink jet head and the ink tank. When the discharge energy is applied to ink, it is arranged to prevent ink from flowing out of the ink jet head excessively, and control to discharge only an appropriate amount of ink from the ink jet head. Also, after ink is discharged from the ink jet head, ink retained in the ink absorbent is carried to the ink jet head. However, in order not to allow ink to flow in continuously without any limit, ink is drawn to the ink absorbent appropriately by means of the negative pressure exerted in the ink absorbent. In this manner, pressure exerted on ink in the ink tank and ink jet head is adjusted by use of the ink absorbent.
FIG. 9 is a perspective view that shows the section of the conventional ink tank. As shown in FIG. 9, an ink absorbent 120 is contained in the containing portion of the ink tank 110. A foaming element, such as urethane sponge, forms the ink absorbent 120. Also, on the wall face of the containing portion of the ink tank 110, plural ribs 101 are formed to extrude perpendicularly from the wall face. Each leading end of the plural ribs 101 is in contact with the ink absorbent 120 to secure the space that becomes each air passage 15 between the wall face having the ribs 101 formed thereon and the ink absorbent 120. In this way, the air is evenly carried to the containing portion of the ink tank 110 through each of the air passages 15 thus secured to make it possible to use ink retained in the ink absorbent 120 efficiently. Also, the ribs 101 are in contact with the ink absorbent 120 to compress the ink absorbent 120, thus presenting an appropriate negative condition.
As shown in FIG. 9, there often utilized a foaming element, such as urethane sponge, for the ink absorbent 120 contained in the conventional ink tank 110. However, depending on the nature of ink to be used, the urethane sponge or some other foaming element chemically reacts upon ink when it is kept for a long time, and in some cases it is not necessarily suitable for use. In recent years, therefore, instead of the foaming element, such as urethane sponge, a laminated fibrous element, which is formed by material having preferably suitable ink preserving property, is sometimes used as the ink absorbent.
FIG. 10 is a perspective view that shows the ink tank 110 that contains the fibrous ink absorbent 121 (hereinafter abbreviated as an ink absorbent), which is formed by a lamination of plural sheet type fibrous element formed by thermally forming the laminated fibrous element, in place of the foaming element, such as urethane sponge.
On the wall face of the ink tank 110 shown in FIG. 10, the ribs 101, which are similar to those shown in FIG. 9, are arranged. In other words, the ribs 101 that extend in the direction parallel to the laminated surface of the fibrous ink absorbent 121. In this case, each of the ribs 101 tends to be buried as shown in FIG. 10 as it enters the absorbent as if inserted into the gap of laminated fibrous material of the ink absorbent 121, because the ribs 101 are in parallel to the laminated surface of the fibrous ink absorbent 121. If the status becomes such as this, any sufficient air passage cannot be secured in the containing portion of the ink tank 110. As a result, the air cannot be carried evenly into the containing portion of the ink tank 110 any more. Also, it becomes difficult for the ribs 101 to secure the condition of pressurized contact with the ink absorbent 121, thus making it uneasy to generate designated negative pressure. Consequently, it often invites the condition that the ink use efficiency of the ink tank 110 is made lower.
On the other hand, FIG. 11 is a perspective view that shows the ink tank 110, which is in a state that as compared with the ink tank shown in FIG. 10, the direction of ribs 101 is rotated at 90 degrees or the direction of fibrous lamination arrangement is rotated at 90 degrees. In other words, on the wall face of the containing portion of the ink tank 110 shown in FIG. 11, the ribs 101 are formed in the direction intersecting with the fibrous lamination surface of the ink absorbent 121.
With the structure thus arranged, such ribs 101 as shown in FIG. 10 do not enter the fibrous lamination surface of the ink absorbent 121 as if inserted along it into the absorbent. Therefore, the air passages 150 can be secured. Nevertheless, there is a tendency that the ink absorbent 121 swells between ribs 101 and 101, and such swelling portions of the ink absorbent 121 approach the wall face of the containing portion eventually. In this case, a part of the ink absorbent 121 is allowed to approach the inner opening of the atmosphere communication port 102, which is communicated with the air passage 150 formed on the wall face to extruded, and which enables the interior of the ink tank to be communicated with the air outside. Then, there is a fear that ink leaks to the outside of the ink tank 110 from the atmosphere communication port 102 due to various causes, such as external vibration, environmental changes, or the like if ink retained in the ink absorbent 121 should exist too closely thereto.
Also, the air passage 150 functions as a buffer pace that temporarily holds ink leaking from the ink absorbent 121 when the ink tank 110 is affected by the environmental changes, such as temperature or pressure changes, and prevents it from leaking to the outside of the ink tank 110 immediately. However, if the ink absorbent 121 swells between ribs 101 and 101 to reduce the volume of the buffer space to make the function of the buffer space insufficient. Then, there is a possibility to allow ink leakage from the atmosphere communication port 102 easier.
In addition, the edge portion of the ink absorbent 121 (near the contact portion with the side face of the ink tank) is caused to swell greater than the other portions (in an image of springing up) depending on the positions of the ribs 101 thus arranged, and there is a possibility to invite such event as the edge portion is in contact with the upper face of the ink tank 110. This may become a cause of ink leakage under such circumstance. Therefore, it is required more that ribs 101 should be arranged closer to the side face of the ink tank 110.
As described above, if ribs 101 should be arranged so as to suppress the selling of the ink absorbent 121 in various locations, intervals between ribs 101 are made narrower eventually, and the resultant buffer spaces formed by the ribs 101 become smaller to make it impossible to demonstrate the buffer function sufficiently. Then, there is a possibility that this becomes a cause of ink leakage. Here, it may be possible to make the volume dedicated for containing the ink absorbent 121 smaller in order to secure the buffer space or make the volume of the tank itself larger to counteract this situation, but this solution is wrong, because the relative importance of the subject is neglected.
Also, for the conventional ink tanks each shown in FIG. 9 to FIG. 11, the ribs 101 are arranged in the form of extending thinly from the wall face of the containing portion. Therefore, the ribs are ease to fall down, and there is a possibility that unless some reinforcement structure is provided, ribs 101 are broken when the ink tank 110 is manufactured: particularly, in the process of welding by use of ultrasonic welding, stress is concentrated on the ribs 101, for example. Also, after manufacture, there is a fear that the ribs 101 are broken in the worst case due to the reaction of the ink absorbent that always acts upon the ribs 101.
Now, in consideration of the problems encountered in the conventional art as described above, the present invention is designed. It is an object of the invention to provide an ink tank having excellent capability of retaining and supplying ink (retaining efficiency and use efficiency), which is capable of suppressing the burying of ribs into ink absorbent when the ink absorbent is formed by laminating fibers and contained in the containing portion of the ink tank, while securing the air passage of the containing portion, as well as keeping the gap (buffer space) between an atmosphere communication port and the ink absorbent appropriately, for the enhancement of ink use efficiency, and also, for the prevention of ink leakage and breakage of ribs.
In order to achieve the object described above, the ink tank of the invention comprises a containing portion for containing an ink absorbent formed by laminated fiber material, and a rib extruding into the interior of the containing portion. For this ink tank, the rib comprises a first directional rib extending diagonally in the direction parallel to the fibrous lamination face of the ink absorbent, and a second directional rib intersecting with the first directional rib.
On the wall face where the rib is formed, an atmosphere communication port may be provided for supplying the air into the interior of the containing portion. Then, it is preferable to provide a guide extruding from the wall face on the circumference of the atmosphere communication port. Further, in this case, it is preferable to make the height of the rib larger than that of the guide.
It is preferable to form the ink absorbent by polypropylene or polyethylene.
Also, the ink tank of the invention, which is detachably mountable on an ink jet head for retaining ink to be supplied to the ink jet head, comprises an ink absorbent structured by laminating fiber material; a containing portion for containing the ink absorbent; an atmosphere communication port for enabling the interior of the ink tank to be communicated with the air outside; and an ink supply port communicated with the ink jet head for supplying ink. For this ink tank, a rib is provided for the side face having the atmosphere communication portion arranged, which comprises a first directional rib diagonally crossing the laminating direction of the fiber material of the ink absorbent, and a second directional rib intersecting with the first directional rib and diagonally crossing the laminating direction of the fiber material of the ink absorbent, and extrudes into the interior of the containing portion.